Sensors for measuring temperature, pressure transducers including temperature sensors and related assemblies and methods

ABSTRACT

Quartz resonator pressure transducers for use in subterranean boreholes include a quartz pressure sensor and an electronic temperature sensor. Temperature sensors include a constant current generator, a proportional to absolute temperature (PTAT) current generator, and a relaxation oscillator. Pressure transducers may include such a temperature sensor. Methods of monitoring pressure in a subterranean borehole may include monitoring a frequency output of a quartz pressure sensor and monitoring a frequency output of an electronic temperature sensor.

TECHNICAL FIELD

Embodiments of the present disclosure relate to sensors for measurement of temperature and, more particularly, to electronic temperature sensors for measurement of temperature for use in, for example, downhole assemblies including one or more quartz resonator sensors and to related assemblies and methods thereof.

BACKGROUND

Thickness shear mode quartz resonator sensors have been used successfully in the downhole environment of oil and gas wells for several decades and are still an accurate means of determining bottom-hole pressure. Quartz resonator pressure sensors typically have a crystal resonator located inside a housing exposed to ambient bottom-hole fluid pressure and temperature. Electrodes on the resonator element coupled to a high frequency power source drive the resonator and result in shear deformation of the crystal resonator. The electrodes also detect the resonator response to pressure and temperature and are electrically coupled to conductors extending to associated power and processing electronics isolated from the ambient environment. Ambient pressure and temperature are transmitted to the resonator, via a substantially incompressible fluid within the housing, and changes in the resonator frequency response are sensed and used to determine the pressure and/or temperature and interpret changes in same. For example, a quartz resonator sensor, as disclosed in U.S. Pat. Nos. 3,561,832 and 3,617,780, includes a cylindrical design with the resonator formed in a unitary fashion in a single piece of quartz. End caps of quartz are attached to close the structure.

Generally, a thickness shear mode quartz resonator sensor assembly may include a first sensor in the form of a primarily pressure sensitive thickness shear mode quartz crystal resonator exposed to ambient pressure and temperature, a second sensor in the form of a temperature sensitive quartz crystal resonator exposed only to ambient temperature, a third reference crystal in the form of quartz crystal resonator exposed only to ambient temperature, and supporting electronics. The first sensor changes frequency in response to changes in applied external pressure and temperature with a major response component being related to pressure changes, while the output frequency of the second sensor is used to temperature compensate temperature-induced frequency excursions in the first sensor. The reference crystal, if used, generates a reference signal, which is only slightly temperature-dependent, against or relative to which the pressure- and temperature-induced frequency changes in the first sensor and the temperature-induced frequency changes in the second sensor can be compared. Such comparison may be achieved by, for example, frequency mixing frequency signals and using the reference frequency to count the signals from the first and second sensors for frequency measurement.

Prior art devices of the type referenced above including one or more thickness shear mode quartz resonator sensors exhibit a high degree of accuracy even when implemented in an environment such as a downhole environment exhibiting high pressures and temperatures. However, each of the quartz resonator sensors that are included in a pressure transducer may be relatively expensive to fabricate, as each quartz resonator sensor must be individually manufactured. Further, the overall size and positioning requirements of the multiple quartz resonator sensors in a pressure transducer may limit the size, shape, and configuration of the assembly.

BRIEF SUMMARY

In some embodiments, the present disclosure includes a quartz resonator pressure transducer for use in a subterranean borehole. The quartz resonator pressure transducer includes a pressure housing comprising at least one chamber, an electronics housing comprising an electronics assembly, and a quartz pressure sensor in communication with the at least one chamber and for measuring pressure of a fluid disposed within the at least one chamber. The electronics assembly is configured to drive the quartz pressure sensor at a selected frequency and to sense a pressure-related frequency response from the quartz pressure sensor. The quartz resonator pressure transducer further includes an electronic temperature sensor electrically coupled to the electronics assembly and configured to output a temperature signal to the electronics assembly.

In additional embodiments, the present disclosure includes a temperature sensor. The temperature sensor includes a constant current generator configured to generate a constant current (ICONST), a proportional to absolute temperature (PTAT) current generator configured to generate a PTAT current, and a relaxation oscillator operably coupled to the constant current generator and the PTAT current generator. The relaxation oscillator is configured to charge and discharge a capacitor responsive to a complementary to absolute temperature current comprising a difference between the constant current and the PTAT current.

In yet additional embodiments, the present disclosure includes a pressure transducer that may include a temperature sensor as described above.

In yet additional embodiments, the present disclosure includes a method of monitoring pressure in a subterranean borehole. The method includes resonating a quartz pressure sensor at at least one frequency with an electronics assembly of a pressure transducer under an applied fluid pressure, monitoring a frequency output of the quartz pressure sensor with the electronics assembly, resonating a quartz reference sensor at at least one frequency with the electronics assembly, monitoring a frequency output of the quartz reference sensor with the electronics assembly, powering an electronic temperature sensor with the electronics assembly, and monitoring a frequency output of the electronic temperature sensor with the electronics assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the present disclosure, various features and advantages of embodiments of the disclosure may be more readily ascertained from the following description of example embodiments of the disclosure provided with reference to the accompanying drawings, in which:

FIG. 1 is a partial cross-sectional view of pressure transducer including an electronic temperature sensor in accordance with an embodiment of the present disclosure;

FIG. 2A is a schematic block diagram of an electronic sensor according to an embodiment of the present disclosure.

FIG. 2B is a schematic block diagram of the current generators of FIG. 2A.

FIG. 2C is a simplified schematic block diagram of the relaxation oscillator of FIG. 2A.

FIG. 3 is a schematic block diagram of an electronic sensor according to an embodiment of the present disclosure.

FIG. 4 is a partial cross-sectional view of pressure transducer including an electronic temperature sensor in accordance with another embodiment of the present disclosure;

FIG. 5 is a side perspective view of an electrical temperature sensor package for use in, for example, the pressure transducer shown in FIG. 4;

FIG. 6 is a side perspective view of the electrical temperature sensor package shown in FIG. 5 with the cover removed;

FIG. 7 is another side perspective view of the electrical temperature sensor package shown in FIG. 5;

FIG. 8 is a partial cross-sectional view of pressure transducer including an electronic temperature sensor in accordance with yet another embodiment of the present disclosure; and

FIG. 9 is a partial cross-sectional view of pressure transducer including an electronic temperature sensor in accordance with yet another embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that depict, by way of illustration, specific embodiments in which the disclosure may be practiced. However, other embodiments may be utilized, and structural, logical, and configurational changes may be made without departing from the scope of the disclosure. The illustrations presented herein are not meant to be actual views of any particular sensor or component thereof, but are merely idealized representations that are employed to describe embodiments of the present disclosure. The drawings presented herein are not necessarily drawn to scale. Additionally, elements common between drawings may retain the same numerical designation.

Although some embodiments of electronic temperature sensors of the present disclosure are depicted as being used and employed in quartz resonator sensor assemblies, persons of ordinary skill in the art will understand that the embodiments of the present disclosure may be employed in any application where electronic measurement of temperature is desirable (e.g., in a downhole assembly or otherwise).

FIG. 1 is a perspective view of a pressure transducer 100 including an electronic temperature sensor. As shown in FIG. 1, the pressure transducer 100 may include a pressure housing 102 having a pressure sensor 104 disposed in a chamber 106 in the pressure housing 102. The chamber 106 in the pressure housing 102 may be in communication with an environment exterior to the pressure transducer 100 in order to determine one or more environmental conditions in the exterior environments (e.g., a pressure and/or temperature of the exterior environment). For example, the chamber 106 may be in fluid communication with an isolation element 108 (e.g., a diaphragm assembly, a bladder assembly, a bellows assembly, and combinations thereof). The isolation element 108 may act to transmit pressure and/or temperature exterior to the pressure transducer 100 to sensors within the pressure transducer 100 (e.g., via a fluid within the pressure transducer). The chamber 106 in the pressure housing 102 may be in fluid communication with isolation element 108 (e.g., via channel 110). Fluid may be disposed in the chamber 106 around the pressure sensor 104, in the channel 110, and in the isolation element 108 to transmit the pressure and/or temperature from the exterior of the pressure transducer 100. In some embodiments, the fluid within pressure transducer 100 may comprise a highly incompressible, low thermal expansion fluid such as, for example, oil (e.g., a Paratherm or sebacate oil). The pressure and thermal expansion of the fluid may be sensed by the pressure sensor 104 (e.g., a quartz crystal sensing element).

As further depicted in FIG. 1, the pressure transducer 100 may include one or more additional sensors that are utilized along with the pressure sensor 102 to determine environmental conditions. The pressure transducer 100 may include a temperature sensor 112 that is at least partially isolated from (e.g., by a pressure feedthrough portion 114 that includes bulkhead 115) from the fluid within the pressure housing 102 that is in communication with the exterior environment. The temperature sensor 112 is utilized to sense the temperature of the exterior environment (e.g., as is it transmitted to temperature sensor 112 through the housing of the pressure transducer 100).

In some embodiments, the pressure transducer 100 may include a reference sensor 116 that is at least partially isolated from (e.g., by the pressure bulkhead 114) from the fluid within the pressure housing 102 that is in communication with the exterior environment. As known in the art, such references sensors 116 may be utilized for comparison with other sensors (e.g., the pressure sensor 102, the temperature sensor 112, or combinations thereof).

An electronics housing 118 is coupled to the pressure housing 102. As depicted, the electronics housing 118 include an electronics assembly 120 that is at least partially isolated from the fluid within the pressure housing 102 that is in communication with the exterior environment. The electronics assembly 120 may be electrically coupled to each of the sensors 102, 112, 116 in the pressure transducer 100 (e.g., via electrical feedthrough pins (not shown)) and may be utilized to operate (e.g., drive) one or more of the sensors 102, 112, 116 and to receive the output of the sensors 102, 112, 116.

In some embodiments, pressure transducers in accordance with the instant disclosure may include methods of fabrication, orientations, quartz structures, electronics, assemblies, housings, reference sensors, and components similar to the sensors and transducers disclosed in, for example, U.S. Pat. No. 6,131,462 to EerNisse et al., U.S. Pat. No. 5,471,882 to Wiggins, U.S. Pat. No. 5,231,880 to Ward et al., U.S. Pat. No. 4,550,610 to EerNisse et al., and U.S. Pat. No. 3,561,832 to Karrer et al., the disclosure of each of which patents is hereby incorporated herein in its entirety by this reference.

As mentioned above, pressure sensor 102 may comprise a quartz crystal sensing element. Conventionally, a pressure transducer having a quartz crystal pressure sensor (e.g., such as that described in U.S. Pat. No. 6,131,462 to EerNisse et al.) will also include a quartz crystal reference sensor and a quartz crystal temperature sensor that are utilized in comparing the outputs of the crystal sensors (e.g., via frequency mixing and/or using the reference frequency to count the signals from the other two crystals). However, in embodiments of the instant disclosure, the temperature sensor 112 may comprise an electronic temperature sensor (e.g., a silicon temperature sensor using, for example, integrated electronic circuits to monitor temperature rather than a sensor exhibiting temperature-dependent variable mechanical characteristics (e.g., frequency changes of a resonator element) such as a quartz crystal resonator). For example, the pressure transducer 100 may include a quartz crystal pressure sensor 102, a quartz crystal reference sensor 116, and an electronic temperature sensor 112 as discussed below in greater detail. As mentioned above, the electronic temperature sensor may utilize electronic circuits to detect temperature as opposed to a mechanical sensor (e.g., a quartz sensor) that monitors one or more mechanical properties of the mechanical sensor (e.g., frequency response of a quartz crystal) to detect temperature.

In some embodiments, the electronic temperature sensor 112 may comprise an integrated circuit (IC) that is utilized, at least in part, to generate a proportional to absolute temperature (PTAT) current (i.e., a PTAT sensor). In some embodiments, such an electronic sensor may provide a temperature sensing range of about 25° C. to 250° C.

FIG. 2A is a schematic block diagram of an electronic sensor 200 according to an embodiment of the present disclosure. The electronic temperature sensor 200 may be an embodiment for the electronic temperature sensor 112 of FIG. 1 or other electronic temperature sensors described herein.

The electronic temperature sensor 200 includes current generators 210 operably coupled with a relaxation oscillator 220 in order to generate an output signal 240 indicating a temperature. In other words, the output signal 240 may be used to determine a temperature of an object. The current generators 210 may be configured to generate a PTAT current (I_(PTAT)) and a relatively constant current (I_(CONST)) that are received by the relaxation oscillator 220. The relaxation oscillator 220 may be configured to generate the output signal 240 responsive to charging and discharging a capacitor (not shown in FIG. 2A) with a complementary to absolute temperature current (I_(CTAT)). The current generators 210 and the relaxation oscillator 220 will be described more fully below with respect to FIGS. 2B and 2C. The electronic temperature sensor 200 may also be referred to herein as a “PTAT sensor” because it generates and uses a PTAT current to contribute to its temperature sensing function. However, it is recognized that the electronic sensor 200 may also generate a constant current that may contribute to its temperature sensing function. Therefore, the term “PTAT sensor” should not be interpreted to be limited to embodiments that only have PTAT current.

FIG. 2B is a schematic block diagram of the current generators 210 of FIG. 2A. The current generators 210 include a first current generator 212 configured to generate I_(PTAT), and a second current generator 216 configured to generate I_(CONST). The first current generator 212 may include an operational amplifier 214 having a first input (e.g., non-inverting input) coupled to resistor R1 and transistor Q1, and a second input (e.g., inverting input) coupled to transistor Q2. The second current generator 216 may include an operational amplifier 218 having a first input (e.g., inverting input) coupled to resistor R2 and transistor Q3, and a second input (e.g., non-inverting input) coupled to resistor R3.

In operation, the first current generator 212 generates I_(PTAT), which also contributes to the generation of a reference voltage V_(REF) (e.g., bandgap voltage) that is received on the node coupled to the first input of the operational amplifier 218 of the second current generator 216. The second current generator 216 generates I_(CONST). Transistors M1, M2, M3, and M4 may assist in the transmission of I_(PTAT) and I_(CONST) to the relaxation oscillator 220.

The values for I_(PTAT) and I_(CONST) may be defined as below:

$\begin{matrix} {{I_{PTAT} = {\frac{kT}{q}{{Ln}\left( \frac{x}{y} \right)}}};} & (1) \\ {I_{CONST} = {\frac{Vref}{R_{3}}.}} & (2) \end{matrix}$

FIG. 2C is a simplified schematic block diagram of the relaxation oscillator 220 of FIG. 2A. The relaxation oscillator 220 may include a comparator 222 that receives a first voltage V_(CAP) and a second voltage V_(TRIP) for comparison and generation of the output signal 240. The output signal 240 may be a digital pulse indicating a temperature, such that the comparator 222 acts as an analog-to-digital converter. The relaxation oscillator 220 may further include additional transistors 224, 226, 228 that are enabled to control current flow of the relaxation oscillator 220. In addition, the relaxation oscillator 220 may include one or more inverters 230 coupled to the output of the comparator 222 that are configured to generate the control signals to the transistors 224, 226, 228.

The first voltage V_(CAP) is the voltage on the capacitor C that is coupled to an input (e.g., non-inverting input) of the comparator 222. The second voltage V_(TRIP) is a voltage on the resistor R4 that is coupled to an input (e.g., inverting input) of the comparator 222. V_(TRIP) may act as a trip point for the comparator 222 as will be discussed more fully below.

The CTAT current (I_(CTAT)) is the difference between I_(CONST) and I_(PTAT) as subtracted at the node coupled to the capacitor C. As a result, I_(CTAT) charges and discharges the capacitor C depending on the phase of operation of the relaxation oscillator 220. The phase of operation may be controlled by the outputs of the comparator 222 and the inverter 230.

During a first phase, the output of the comparator 222 may be unasserted (e.g., a logic low) and the output of the inverter 230 may be asserted (e.g., a logic high). As a result, the transistors 224 and 228 may be enabled and the transistor 226 may be disabled. At the node of the capacitor C, the capacitor may be charging (i.e., V_(CAP) may be increasing), with I_(CTAT) sourcing the current of the capacitor C. Because transistor 228 is enabled, the current K*I_(CONST) flows through resistor R4. Thus, the current flowing through resistor R4 may be (K+M)*I_(CONST) because of contributions from both current paths M*I_(CONST) and K*I_(CONST). Therefore, V_(TRIP) may have a first level during the first phase:

V _(TRIP 1)=(K+M)I _(CONST) *R ₄   (3).

As V_(CAP) increases and rises above V_(TRIP1), the output of the comparator 222 switches, and the capacitor begins discharging. During this second phase of the comparator 222, the output of the comparator 222 may be asserted (e.g., a logic high) and the output of the inverter 230 may be unasserted (e.g., a logic low). As a result, the transistors 224 and 228 may be disabled and the transistor 226 may be enabled. At the node of the capacitor C, the capacitor may be discharging (i.e., V_(CAP) may be decreasing), with I_(CTAT) sinking the current of the capacitor C. In addition, because transistor 228 is disabled, the current K*I_(CONST) may not flow through resistor R4. Thus, the current flowing through resistor R4 may be M*I_(CONST) because the only contribution may come from the current paths M*I_(CONST). Therefore, V_(TRIP) may have a second level during the second phase:

V _(TRIP 2) =MI _(CONST) *R ₄   (4).

Thus, the second level (V_(TRIP2)) may be less than the first level (V_(TRIP1)) that is responsive to additional current (K*I_(CONST)) either flowing through resistor R4 or not flowing through resistor R4 depending on the phase of the output of the comparator 222. As a result, the output signal 240 may have a sufficient peak-to-peak voltage for detection responsive to the charging and discharging of the capacitor C.

In summary, V_(CAP) may either charge or discharge responsive to the I_(CTAT), which is the difference of I_(CONST) and I_(CTAT.) Including a constant current (I_(CONST)) in that determination may enable increased the sensitivity and control of the offset and the slope control of the electronic temperature sensor 200 by controlling both the resistor R4 and capacitor C as potentiometers. In addition, the comparator 222 may operate between at least two trip points that are responsive to the phase of the relaxation oscillator 220 by adding a current (e.g., K*I_(CONST)) to raise the trip point voltage during one of the phases.

As a result, the output signal 240 may indicate a given temperature. For example, the frequency of the output signal 240 may be used to determine the temperature of an object. The frequency may be measured and correlated to a temperature, but may also be understood as:

$\begin{matrix} {F_{T} = {\frac{I_{CONST} - I_{PTAT}}{2\; {C\left( {V_{{TRIP}\; 1} - V_{{TRIP}\; 2}} \right)}}.}} & (5) \end{matrix}$

FIG. 3 is a schematic block diagram of an electronic temperature sensor 300 according to an embodiment of the present disclosure. The electronic temperature sensor 300 may be an embodiment for the electronic temperature sensor 112 of FIG. 1 or other electronic temperature sensors described herein. The electronic temperature sensor 300 may include the current generators 210 and the relaxation oscillator 220 that are configured to operate generally as described above. The electronic sensor 300 of FIG. 3 further includes an example of a configuration that includes transistors M5-M19 that perform the current source, sink, and mirroring functions that are described above in a more simplified form. It is contemplated that the current source, sink, and mirroring functions may be implemented by various configurations, and that the example shown herein is presented as an example of such an implementation of embodiments of the present disclosure.

As shown in FIG. 3, transistors M8, M10, M14, and M15 may perform the functionality described in FIG. 2C with respect to transistors 224, 226. As discussed above, the output of the comparator 222 may be coupled to one or more inverters 230, 232. In the embodiment shown in FIG. 3, a first inverter 230 and a second inverter 232 are coupled to the output of the comparator 222. During a first phase, the output of the comparator 222 may enable transistors M8 and M15, while transistors M10 and M14 are disabled. As a result, I_(CONST) sources current from transistor M11 and I_(PTAT) sinks current from transistor M17 causing the net difference between the two currents to charge the capacitor C. In addition, transistor M6 is enabled causing additional current to flow through resistor R4 and V_(TRIP) to have a relatively higher trip point. During the second phase, the output of the first transistor 230 may enable transistors M10 and M14, while transistors M8 and M15 are disabled. As a result, I_(PTAT) sources current from transistor M11, and I_(CONST) sinking current from transistor M17 causing the net difference between the two currents to discharge the capacitor C. In other words, during the two phases the currents I_(PTAT) and I_(CONST) switch positions. As temperature increases, I_(CTAT) decreases. As temperature decreases, I_(CTAT) increases. The temperature may be detected as indicated by the output signal 240.

FIG. 4 is a partial cross-sectional view of pressure transducer 400 including an electronic temperature sensor 412. The pressure transducer 400 may be the same or somewhat similar to and may include one or more features of the pressure transducer 100 discussed above with regard to FIG. 1. As shown in FIG. 4, the pressure transducer 400 may include a pressure housing 402 having a quartz crystal pressure sensor 104 disposed therein and the electronic temperature sensor 412 and a quartz crystal reference sensor 116. An electronics housing 418 of the pressure transducer 400 may be coupled to the pressure housing 402 and include the electronics assembly 120 for operating the sensors 104, 412, 116.

As depicted in FIG. 4, the electronic temperature sensor 412 may comprise a silicon temperature chip (e.g., a PTAT sensor) and may be disposed in an electronic temperature sensor assembly 422. For example, the electronic temperature sensor assembly 422 may comprise the electronic temperature sensor 412 disposed in a transistor outline (TO) package 424. FIGS. 5, 6, and 7, show a side perspective view of the electronic temperature sensor assembly 422, a side perspective view of the electronic temperature sensor assembly 422 with a cover 426 of the transistor outline package 424 removed, and another side perspective view of the electronic temperature sensor assembly 422, respectively. Referring to FIGS. 5, 6, and 7, the electronic temperature sensor assembly 422 includes the electronic temperature sensor 412 housed within the transistor outline package 424. For example, the electronic temperature sensor 412 is coupled to a base portion 428 of the transistor outline package 424 and positioned between the base portion 428 and the cover 426, which extends around a majority of the base portion 428 and the electronic temperature sensor 412.

The electronic temperature sensor 412 is electrically connected to one or more feedthrough pins 430 (e.g., via one or more bond wires 432) that may be electrically coupled to the electronics assembly 120 (FIG. 4) to provide electrical communication between the electronic temperature sensor 412 and the electronics assembly 120.

Referring back to FIG. 4, the electronic temperature sensor 412 (e.g., the electronic temperature sensor assembly 422 including the electronic temperature sensor 412 in the transistor outline package 424) may be positioned in the pressure feedthrough portion 414 of the pressure transducer 400 proximate the pressure housing 402 and the pressure sensor 104 and adjacent the bulkhead 415. For example, the electronic temperature sensor assembly 422 may be positioned between the pressure sensor 104 and the reference sensor 116 (e.g., between the reference sensor 116 and the bulkhead 415 separating the pressure sensor 102 from the reference sensor 116 and the temperature sensor 412). In some embodiments, the electronic temperature sensor assembly 422 may be at least partially embedded in the bulkhead 415.

In some embodiments, the electronic temperature sensor assembly 422 and the reference sensor 116 may be positioned longitudinally adjacent to each other (e.g., along a longitudinal axis L₄₀₀ of the pressure transducer 400). In such an embodiment, the electronic temperature sensor assembly 422 may be positioned relatively closer to the pressure sensor 104 than the reference sensor 116. Such positioning may enable the temperature sensor 412 to sense temperature substantially similar to the temperature at the pressure sensor 102. In some embodiments, such positioning may reduce transients experienced by one or more portions of the pressure transducer 400 (e.g., the temperature sensor 412) due to temperature gradients within the pressure transducer 400.

In other embodiments, such as that shown in FIG. 1, the electronic temperature sensor assembly 422 and the reference sensor 116 may be positioned laterally adjacent to each other (e.g., in a direction transverse to the longitudinal axis L₄₀₀ of the pressure transducer 400).

In some embodiments, the reference sensor 116 may also be housed in a transistor outline package 434. In such an embodiment, the transistor outline package 424 of the electronic temperature sensor assembly 422 may be relatively smaller in size than (e.g., having a smaller volume than) the transistor outline package 434 of the quartz crystal reference sensor 116.

FIG. 8 is a partial cross-sectional view of pressure transducer 500 including an electronic temperature sensor 512. The pressure transducer 500 may be the same or somewhat similar to and may include one or more features of the pressure transducers 100, 400 discussed above with regard to FIGS. 1 and 4 through 7. As shown in FIG. 8, the pressure transducer 500 may include a pressure housing 502 having a quartz crystal pressure sensor 104 disposed therein and the electronic temperature sensor 512 and a quartz crystal reference sensor 116. An electronics housing 518 of the pressure transducer 500 may be coupled to the pressure housing 502 and include the electronics assembly 520 for operating the sensors 104, 512, 116.

As depicted in FIG. 8, the electronic temperature sensor 512 may comprise a silicon temperature chip (e.g., a PTAT sensor) and may be positioned in the electronics housing 518 of the pressure transducer 500. For example, the electronic temperature sensor 512 may be positioned at (e.g., on or integrated with) the electronics assembly 520 in the electronics housing 518 of the pressure transducer 500. In some embodiments, the electronic temperature sensor 512 may be coupled (e.g., electrically and mechanically coupled) to an application specific integrated circuit (ASIC) of the electronics assembly 520 that also operates and monitors the quartz crystal pressure sensor 104 and the quartz crystal reference sensor 116. In other words, the electronic temperature sensor 512 may be positioned on the ASIC of the electronics assembly 520, which assembly 520 also performs one or more of the functions of driving the quartz crystal pressure sensor 104 and the quartz crystal reference sensor 116 at one or more selected frequencies, receiving the output (e.g., frequency output) form the quartz crystal pressure sensor 104 and the quartz crystal reference sensor 116, monitoring the output (e.g., frequency output) of the electronic temperature sensor 512, and powering the electronic temperature sensor 512.

The reference sensor 116 may be positioned between the electronic temperature sensor 512 and the pressure sensor 104 (e.g., in a direction along a longitudinal axis L₅₀₀ of the pressure transducer 500). Stated in other way, the electronic temperature sensor 512 may be positioned on a first end portion of the pressure transducer 500 in the electronics housing 518. The pressure sensor 104 may be positioned on a second end portion of the pressure transducer 500, opposing the first end portion, in the pressure housing 502. The reference sensor 116 may be positioned between the electronic temperature sensor 512 in the electronics housing 518 and the pressure sensor 104 in the pressure housing 502 (e.g., in the pressure housing 502 separated from the pressure sensor 104 by the bulkhead 515.

FIG. 9 is a partial cross-sectional view of pressure transducer 600 including an electronic temperature sensor 612. The pressure transducer 600 may be the same or somewhat similar to and may include one or more features of the pressure transducers 100, 400, 500 discussed above with regard to FIGS. 1 and 4 through 8. As shown in FIG. 9, the pressure transducer 600 may include a pressure housing 602 having a quartz crystal pressure sensor 104 disposed therein and the electronic temperature sensor 612 and a quartz crystal reference sensor 116. An electronics housing 618 of the pressure transducer 600 may be coupled to the pressure housing 602 and include the electronics assembly 120 for operating the sensors 104, 612, 116.

As depicted in FIG. 9, the electronic temperature sensor 612 (e.g., a silicon temperature chip such as a PTAT sensor) may be positioned in the pressure housing 602 of the pressure transducer 600 between the pressure sensor 104 and the reference sensor 116 (e.g., in a direction along a longitudinal axis L₆₀₀ of the pressure transducer 600). For example, the electronic temperature sensor 612 may be positioned proximate the pressure sensor 102 in the pressure housing 602 on the same side of bulkhead 615 as the pressure sensor 102. The electronic temperature sensor 612 may be positioned within a chamber 606 in the pressure housing 602 in which the pressure sensor 102 and the fluid for communication of one or more of pressure and temperature from an exterior environment is disposed. Stated in other way, the electronic temperature sensor 612 disposed directly in (e.g., in direct thermal communication with) a working fluid of the pressure transducer 600 rather than being isolated from the working fluid as discussed above. For example, the electronic temperature sensor 612 may be coupled to a first side of the bulkhead 615 adjacent the pressure sensor 102 and may be electrically coupled to one or more feedthrough pins 624 that electrically couple the electronic temperature sensor 612 to the electronics assembly 120. The reference sensor 116 may be positioned on a second side of the bulkhead 615 opposing the first side (e.g., proximate the electronics housing 618). In such an embodiment, the electronic temperature sensor 612 may be placed in direct communication (e.g., fluid communication) with the working fluid of the pressure transducer 600 enabling the electronic temperature sensor 612 to directly measure the temperature of the working fluid (which temperature is transmitted to the working fluid by the environment exterior to the pressure transducer 600). Such positioning may enable the temperature sensor 612 to sense temperature substantially similar to the temperature at the pressure sensor 102. In some embodiments, such positioning may reduce transients experienced by one or more portions of the pressure transducer 600 (e.g., the temperature sensor 612) due to temperature gradients within the pressure transducer 600.

In some embodiments, the electronic temperature sensor 612 may be positioned within an opening formed in spacer 626 (e.g., a dielectric spacer that at least partially isolates the pressure sensor 102 from the bulkhead 615) positioned on the same side of the bulkhead 615 as the pressure sensor 102.

Embodiments of the present disclosure may be particularly useful in providing electronic temperature sensors having a robust applicability in many different applications. For example, such electronic temperature sensors, when implemented in a pressure transducer for downhole pressure-sensing applications, may provide additional flexibility in positioning the electronic temperature sensor within the pressure transducer and may improve the reliability, sensitivity, and ease of maintenance and replacement as compared to pressure transducers having a quartz crystal temperature sensor.

While the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the disclosure encompasses all modifications, variations, combinations, and alternatives falling within the scope of the disclosure as defined by the following appended claims and their legal equivalents. 

1. A quartz resonator pressure transducer for use in a subterranean borehole, comprising: a pressure housing comprising at least one chamber; an electronics housing comprising an electronics assembly; a quartz pressure sensor in communication with the at least one chamber and for measuring pressure of a fluid disposed within the at least one chamber, wherein the electronics assembly is configured to drive the quartz pressure sensor at a selected frequency and to sense a pressure-related frequency response from the quartz pressure sensor; and an electronic temperature sensor electrically coupled to the electronics assembly and configured to output a temperature signal to the electronics assembly.
 2. The quartz resonator pressure transducer of claim 1, wherein the temperature signal comprises a frequency signal.
 3. The quartz resonator pressure transducer of claim 1, wherein the electronic temperature sensor comprises a silicon temperature sensor.
 4. The quartz resonator pressure transducer of claim 3, wherein the electronic temperature sensor comprises a proportional to absolute temperature (PTAT) current generator configured to generate a PTAT current.
 5. The quartz resonator pressure transducer of claim 4, wherein the electronic temperature sensor further comprises a constant current generator configured to generate a constant current.
 6. The quartz resonator pressure transducer of claim 5, wherein the electronic temperature sensor comprises a relaxation oscillator that is coupled to each of the PTAT current generator and the constant current generator, the relaxation oscillator configured to generate an output signal responsive to a complementary to absolute temperature current comprising a difference between the constant current and the PTAT current.
 7. The quartz resonator pressure transducer of claim 5, wherein the electronic temperature sensor has a trip point for charging and discharging a capacitor, the trip point responsive to the constant current.
 8. The quartz resonator pressure transducer of claim 1, further comprising a pressure bulkhead for separating the pressure housing from the electronics housing, wherein the electronic temperature sensor is at least partially embedded in the pressure bulkhead.
 9. The quartz resonator pressure transducer of claim 1, wherein both the quartz pressure sensor and the electronic temperature sensor are positioned to be at least partially disposed within the fluid disposed within the at least one chamber.
 10. The quartz resonator pressure transducer of claim 1, wherein the electronic temperature sensor is disposed in the electronics housing.
 11. The quartz resonator pressure transducer of claim 10, wherein the electronic temperature sensor is disposed on an integrated circuit of the electronics assembly in the electronics housing.
 12. The quartz resonator pressure transducer of claim 10, further comprising a quartz reference sensor positioned between the electronic temperature sensor and the quartz pressure sensor.
 13. The quartz resonator pressure transducer of claim 1, further comprising: a quartz reference sensor; and a pressure bulkhead for separating the pressure housing from the electronics housing, wherein the electronic temperature sensor is positioned between the quartz reference sensor and the quartz pressure sensor.
 14. The quartz resonator pressure transducer of claim 13, wherein the electronic temperature sensor and the quartz reference sensor are positioned on a first side of the pressure bulkhead and the quartz pressure sensor is positioned on a second side of the pressure bulkhead opposing the first side.
 15. The quartz resonator pressure transducer of claim 14, wherein the electronic temperature sensor and the quartz reference sensor are each disposed in a transistor outline (TO) package.
 16. The quartz resonator pressure transducer of claim 15, wherein the transistor outline (TO) package of the electronic temperature sensor has a volume that is less than a volume of the transistor outline (TO) package of the quartz reference sensor.
 17. The quartz resonator pressure transducer of claim 13, wherein the quartz reference sensor is positioned on a first side of the pressure bulkhead and the quartz pressure sensor and the electronic temperature sensor are positioned on a second side of the pressure bulkhead opposing the first side.
 18. A temperature sensor, comprising: a constant current generator configured to generate a constant current (I_(CONST)); a proportional to absolute temperature (PTAT) current generator configured to generate a PTAT current; and a relaxation oscillator operably coupled to the constant current generator and the PTAT current generator, and configured to charge and discharge a capacitor responsive to a complementary to absolute temperature current comprising a difference between the constant current and the PTAT current.
 19. The temperature sensor of claim 18, wherein the relaxation oscillator includes a comparator having a first input and a second input, the first input configured to receive a voltage on the capacitor, and the second input configured to receive a trip voltage.
 20. The temperature sensor of claim 19, wherein the relaxation oscillator is configured such that: during a first phase of the relaxation oscillator, the constant current sources current to the capacitor and the PTAT current sinks current from the capacitor; and during a second phase of the relaxation oscillator, the PTAT current sources current to the capacitor and the constant current sinks current from the capacitor.
 21. The temperature sensor of claim 19, wherein relaxation oscillator is configured to raise the trip voltage during a first phase of the relaxation oscillator, and lower the trip voltage during a second phase of the relaxation oscillator.
 22. A pressure transducer, comprising: at least one pressure sensor; and the temperature sensor of claim
 18. 23. A method of monitoring pressure in a subterranean borehole, comprising: resonating a quartz pressure sensor under an applied fluid pressure at at least one frequency with an electronics assembly of a pressure transducer; monitoring a frequency output of the quartz pressure sensor with the electronics assembly; resonating a quartz reference sensor at at least one frequency with the electronics assembly; monitoring a frequency output of the quartz reference sensor with the electronics assembly; powering an electronic temperature sensor with the electronics assembly; and monitoring a frequency output of the electronic temperature sensor with the electronics assembly.
 24. The method of claim 23, further comprising measuring a temperature within the pressure transducer with a proportional to absolute temperature (PTAT) sensor.
 25. The method of claim 23, further comprising temperature-compensating the monitored frequency output of the quartz pressure sensor with the electronics assembly using the frequency output of the electronic temperature sensor. 